In conventional rotating rigid disk files, each of the read/write transducers (or heads) is supported on a carrier (or slider) which rides on a cushion or bearing of air above the surface of its associated disk when the disk is rotating at its operating speed. The slider is connected to a linear or rotary actuator by means of a relatively fragile suspension. There may be a stack of disks in the disk file with the actuator supporting a number of sliders. The actuator moves the sliders radially so that each head may access the recording area of its associated disk surface. In these conventional disk files the slider is biased towards the disk surface by a small force from the suspension. Because the slider is in contact with the disk surface from the time the disk file is turned on until the disk reaches a speed sufficient to cause the slider to ride on the air-bearing, and again in contact with the disk surface when the disk file is turned off and the rotational speed of the disk falls below that necessary to create the air-bearing, such disk files are referred to as contact start-stop (CSS) disk files. In CSS disk files it is not necessary that the disk surface be extremely smooth since the slider is only in contact during start and stop operations. Instead, it is desirable to texture the disk surface to reduce the static friction between the slider and the disk when the slider is at rest on the disk surface.
In addition to the above-described conventional CSS magnetic recording disk files, "contact" recording rigid disk files have been proposed. In one type of contact recording, referred to as "liquid bearing" contact recording, the head-disk interface includes a liquid film as a liquid bearing between the transducer carrier and the disk. An example of this type of contact recording disk file is described in assignee's pending application, U.S. Ser. No. 264,604, filed Oct. 31, 1988, and published May 9, 1990 as European published application EP 367510. In another type of contact recording, referred to as "dry" contact recording, the disk file uses an integrated head-suspension which makes physical contact with the disk surface during read and write operations. In this type of head-suspension, as described for example in U.S. Pat. No. 5,041,932, a portion of the head actually wears away due to frictional contact with the disk over the life of the disk file. In both types of contact recording disk files it is necessary, because of the close head-disk spacing, to make the disk surface extremely smooth.
One type of disk which has been used in rigid disk files is a thin film metal alloy disk which typically comprises a substrate, such as an aluminum-magnesium (AlMg) alloy with a nickel-phosphorous (NiP) surface coating, a cobalt-based alloy, such as a CoPt or CoNi alloy, sputter deposited as the magnetic layer on the substrate, and a protective overcoat, such as a sputter-deposited amorphous hydrogenated carbon film, formed on the magnetic layer. In addition to the magnetic layer and the protective overcoat, thin film disks may also include a sputter deposited underlayer, such as a layer of chromium (Cr), chromium-vanadium (CrV) or tungsten (W), between the substrate and the magnetic layer and a sputter deposited adhesion layer, such as a Cr, W or titanium (Ti) layer, between the magnetic layer and the protective overcoat. While this conventional disk is adequate for use in CSS disk files, it has been found that when the AlMg-NiP substrate is made very smooth, as required if the disk is to be used in contact recording disk files, it is not possible to manufacture the disk in the conventional manner and still achieve the required disk coercivity.
Thus what is needed is an improved thin film metal alloy magnetic recording disk, based upon the conventional disk technology, which is usable in contact recording disk files so that such files can have both the required smooth head-disk interface and disk coercivity.